Add spell checking core methods.

Bug: 4176026
Change-Id: Ic6ea3e084b3ebacfc5fd998d2c7b0130f7b0ec48
diff --git a/java/proguard.flags b/java/proguard.flags
index 914bd75..9094be4 100644
--- a/java/proguard.flags
+++ b/java/proguard.flags
@@ -22,3 +22,7 @@
 -keep class com.android.inputmethod.latin.Utils {
   boolean equalsIgnoreCase(...);
 }
+
+-keep class com.android.inputmethod.latin.spellcheck.SpellChecker {
+  *;
+}